One of the most amazing things to see on a night dive is bioluminescence. Cover your torch, wave your hands around, and watch little dots of neon blue light appear and disappear in front of your eyes like magic. Sometimes, you can see this phenomenon when you are walking along the beach at night, when the waves come in and the water glows with the same specks of neon blue light, as seen in the photo below. But what is it and why does it happen?

This is a group of plankton called dinoflagellates. They are single-celled plankton commonly found living in the world’s oceans, drifting on the surface or in the water column and have the ability to produce bioluminescence. This means that they can produce light as a result of chemical reactions taking place in their bodies.

The word bioluminescence comes from the Greek bios for “living” and the Latinlumen “light”. Hence, what you are seeing is literally living light!

You’ve probably seen this phenomenon in other creatures before – think of fireflies. You might have also combined chemicals yourself to create light – think about cracking a glow stick to make it light up.

So why do these plankton produce this light? Some scientists believe that this is a defense mechanism, since they emit their bluish glow only when disturbed, either by waves crashing onto the beach, a boat’s wake, a kayaker’s paddle splashing into the water, or a diver’s movement underwater. The theory is that the glow attracts larger fish to come eat the smaller fish that were feeding on the plankton. Your underwater light show is their way of calling out for help. Imagine that!